Boro-phosphoric acid and method of preparing the same



Fatentecl May 8, 1945 BQDRQ PHOSPHOEIC [161]) AND METHOD F PEIEPARHNG THE SAME Leonarri H. England, Winona, Minn.

its iii-owing. Amililcatlon Mar 17, rest, Serial No, 393,938

6 Claims. ((Cl. 23-lii6) This invention relates to the provision and prodecision of phosphorus pentoxide derivatives and has as a general object the provision and preparation of a novel bore-phosphoric acid and a method of preparing various salts thereof.

A more specific object of the invention is the provision of a novel powdery non-hygroscopic acid comprising acirl oxide groups of boron and phosphorus together with certain molecular proportions of water.

Another object of the invention is the provision of a novel hero-phosphoric acid which has a relatively great capacity for neutralizing bases and which can be readily stored and handled as othernorr-corrosive powders without requiring expensive rubber-coated or rubber-lined equipment and containers.

A further object of the invention is to provirle such an acid as a source of certain useful derivatives including heron phosphate, ammolliilm salts of the acid, and sodium salts thereof as well as the salts of other cilia-tine earth metals.

The invention has as another object the provision of a-novel and improved method of oreparing the novel acid anti its salts and other derivatives involving e, reaction between chosphoros pentoizirle and hcric aciii,

Other objects oi the invention will become apparent from the following description of a preferred embodiment of the invention.

It is generally helieveothat dry powdered horic acid does not react with dry powdered nhosphorus pentoiritie, and further that if water added to the mixture or such powders, one of the following results Wi'il he obtained:

(cl, The formation ci a nro oortionsi amount of meta=phcsphoric acizi, HPQs, with horic acid, Milli) 3 according to the equation,

(b) If more waterv he added, the formation of a larger proportion oi either or both oi the phosphoric acids, meta=, moi, one (lllihfi 4 with lactic acid or with horic oxide, Elem, eccorei= ing tothe following respective equations:

Notwithstening that general belief, I have dis: covered a powdery non-hygroscopic acid comprising poly-acid oxide groups of boron one M41635- phoros together with certain meleciiiar proportions of water, enclhow to make such an acid and derivatives thereof by reactingcommercial dry powdered lactic aciol with commercial dry powdered ohosphcrus peotoxioe, The novel acid has the formula B4QNH'3P2Q6)! cool therefore hes been termed tetrabcrohypophosphorlc acid. Approximately two molecular equivalents of the iii phosphorus pentoxide P205. to about four molecular equivalents of the boric acid B(0H); are employeri'in the reaction which is represented by the following equation: I

While. I do not wish the invention limited to any theory oi the reactions which may be involved, in view of the general belief stated above, it might he well to point out by way of possible explanation that I believe the two molecular equivalents of the phosphorus pentoxide, 2P2Oc, abstract from the four molecular equivalents of the horic acid, QWOHM, three molecular equivalents of water, Thus the boron oxide groups may be converted into one molecular equivalent of pyrmhcric aciri, M48295, and one molecular equivalent oi meta-ooric acid, [23204 according to the following equation:

(1) 2 tetorii s ritetot+irsezoi- -anio Uncier the conditions of the reactions to be more fully riescrihecl presently, the nyroand meta heric acids ,croieahiy combine to term one molecular equivalent of tetra-Faerie ecicl, $123401, with the iiheration of two molecrzier equivalents of water which e tree to eeencrate. This reactime may he representeti hy the toiletries: equa- The two molecular ergnivalentsof the chosphoruis cent-oxide, iiPzUs, with the three molecular equivalents of water (see Equation 1 above) abstracted; irons the Your molecular equivalents of the hcric acici, eiiifiii ii a, I believe, form one molecular eqoiraientjoi tetrawhcsnhoric acid, HePrQrs, eccoroirie; to the equation:

That tetra-phosphoric ecid, topic probably combines with the tetro=hcric acid, HzBsQr to form one molecular ec uivcient of the novel acid herein celleci tetrahorohgvnorihosnhciic acid,

BMQflHiE- mcle, lice-retiree one molccuier equivalent of writer which is free to evaporate and which is protects formed by the seneretins ofi of two hydro-gen atoms irom the tetra==horic acicland one oxygen atom from the tetra gihcsohoric acid reducing the latter to the hygiwohosohoric acid,

Such reaction is represented by the following equation: Y

throughout the entire mixture with a hissing noise and the evolution of fumes and results in a generous yield of the novel hero-phosphoric acid.

For example, 56 grams of commercial powdered phosphorus pentoxide are intimately mixed with 50 grams of commercial powdered boric acid. After so mixing, one or two drops of waterv are added to the mixed powderswhereupon the vigorous progressive reaction occurs as just described.

" The resulting mass is slightly moist and weighs a little less than the total weight of the comi ponents. After drying in. a hot air oven, at a temperature less than 100 degrees C.,-the yield is 95 grams of the tetraborohypophosphoric acid The novel acid so made is a dry non-hygros copic powder and hence can be handled and stored as any non-corrosive powder without vem-- ploying expensive rubber-lined equipment and containers. In general it has the properties of ortho-phosphoric acid and in addition it has other'properties not possessed byv ortho-phosphoric acid. It has a relatively great capacity to neutralize bases. For example, 17 /2 grams of sodium carbonate was required to be added to grams of the novel acid to develop an alkaline re: action with phenolphthalein.

Th novel acid has many desirable derivatives. One such derivative is boron phosphateBPOr. Boron phosphate has valuable applications as a catalyst in organic reactions and especially in thermal treatments of petroleum derivatives and as a double acid oxide component of vitreous enamels and ceramic products. 'It is made ac-- cording to the invention by heating, for'example,

' 10 grams of the novel acid for one-half hour at red heat with a. yield of 8.9 grams of boron phosphate. The reaction is I s modmmom-anrowamo.

The water soluble "form of boron phosphate is made when the temperature employed in the reaction J'ust described is less than 400 degrees C.

but not less than about 200 degrees C. So made, the resulting boron phosphate slowly hydrolyzes and dissolves in water. The water and acid insoluble form of boron phosphate is 'made by em- Dloying in the above mentioned reaction a ternperature above 400' degrees C. The resultin boron phosphate is not only water insoluble but is also infusible at white heat.

The ammonium, sodium, and other alkaline- Ease salts of the novel acid are made in general (a) Neutralizing or combining such bases with-- the novel acid in aqueous solution; or

b) Combining the alkaline-base with boric acid and,.with the borate thus obtained, reactin phosphorus pentoxide in the manner described hereinabove for the preparation of the borophosphoric acid; or

(c) In some cases mixingand heating the alkaline base, boric acid, and phosphorus pentoxide without first making the borate.

For example, crystalline disodium phosphate is heated unti1 it melts or dissolves in its water of crystallization. Boric acid is then dissolved therein. 'I'he solution so prepared does not rec ystallize upon-cooling but remains as a syrupy-liquid.

at the ebullition point. The product made by heating below the ebullition point diflers from the other in that it is very slowly soluble, even in hot water, whereas ,when prepared by heating at the ebullition point, the resulting salt is so instantly soluble in water that the escape of occluded air is audible when a lump of it is dropped into water.

Sodium salts of the novel acid have thus been prepared ranging from those-having a sharp acid reaction to those which are alkaline insolution. Such salts which are alkaline have valuable detergent, emulsification, and water conditioning properties and may be incorporated in water solubl soaps. Those which are acid exhibit a de-- 'gree of tackiness or adhesiveness that is truly remarkable. In addition the sodium salts are useful in coating filters used in air conditionin apparatus by immersing the filters in water solutions of the salts and thereafter evaporating the excess water.

Similarly, the products of thisreaction between boric acid and mono-ammonium phosphate, di-

ammonium phosphate, or mixtures of sodium and ammonium phosphates .are made and the resulting salts exhibit either an acid or alkaline reaction in accordance with the ratio of the bases and acid oxide groups which may be present. Such I salts have a syrupy consistency which persists even after baking at high temperatures. The resistance to crystallization under such conditions makes these salts useful as the disp 8 in fire-proofing or fire-resisting compounds.

' While a specific embodiment of the invention has been described, it will be understood that the invention is not limited to the precisedetails hereinabove set forth by way oi illustration, but instead what is claimed anddesired'to be secured by United States Letters Patent is:

1. The method of producing a, water soluble phosphorus-boron containing composition which comprises reacting boric acid with phosphorus pentoxide at a temperature below 400 C. in the presence of a reaction product of water and phosphorus-pentoxide.

2. The method of producing a water soluble phosphorus-boron containing composition which comprises reacting boric'acid with phosphorus pentoxide at a temperature below 200 C. in the presence .of a reaction product of water and phorus pentoxide.

3. The method of producing a water soluble acid anhydride having the empirical formula BPOi'which comprises heating at a temperature of between 200 C. and 400 C., a compound obphostained by reacting boric acid with phosphorus pentoxide'at a temperature below 200 C.

4. A compound selected from the group consisting of a water soluble compound obtained by reacting boric acid with phosphorus pentoxide at a temperature below 200C, and salts thereof.

5. A water soluble composition having the empirical fOrInu1a-H6P4B40i9 obtained by reactin boric acid with phosphorus pentoxide at a temperature below 200 C. o

6. A' water soluble acid anhydride having the empirical formula BPO4 obtained by heating at a If that solution be heated to a temperature below the ebullition point, a diflerentsalt is obtained from that, obtained where the temperature is kept temperature between 200 C. and 400 C., a water soluble compound obtained byv reacting boric acid with phosphorus pentoxide at a temperature be-.

low' 200 C.

. LEONARD H. ENGLUND. 

